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Goodver
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Why momentum of phonons called quasimomentum? Is it due to the fact that wavenumber of vibrations confined in a first Brillouin zone, and therefore can not have an arbitrary value as "usual" momentum?
DrDu said:The momentum of phonons isn't called quasimomentum. The true momentum of phonons is 0. While the true momentum is a consequence of translational invariance, quasi- or crystal-momentum is a consequence of the permutational symmetry of the atoms in the underlying crystal. See Ashcroft and Mermin, specifically one of the appendices.
Phonon quasimomentum is a concept used in solid-state physics to describe the momentum of a phonon, which is a quantized vibration of atoms in a crystal lattice. It is important because it helps us understand the behavior of phonons, which play a crucial role in many physical phenomena, such as heat conduction and electrical conductivity in materials.
The crystal lattice structure of a material determines the allowed values of phonon quasimomentum. This is because the lattice structure dictates the periodicity of the atomic vibrations, which in turn affects the momentum of the phonons.
Yes, the quasimomentum of phonons can be indirectly measured through various experimental techniques, such as neutron scattering or Raman spectroscopy. These methods allow us to study the properties of phonons and their behavior in different materials.
The phonon quasimomentum affects thermal conductivity in materials by determining the rate at which phonons transfer thermal energy. In materials with a highly ordered crystal lattice, phonons with similar quasimomentum can travel long distances without scattering, leading to efficient thermal conductivity. In disordered materials, phonons with different quasimomenta can scatter more frequently, reducing thermal conductivity.
Yes, understanding phonon quasimomentum has practical applications in the development of new materials with improved thermal and electrical properties. It also plays a crucial role in the design of electronic devices, such as transistors and sensors, which rely on the efficient transport of phonons.